1. Field of the Invention
The present invention relates to a switching power supply unit configured to produce switching output, which is obtained by switching a DC input voltage, at an output winding of a voltage conversion transformer.
2. Background Art
Various types of DC/DC converters have been proposed for a switching power supply unit, and provided for practical use in the past. Most of the DC/DC converters are in a type where a DC input voltage is subjected to switching by switching operation of a switching circuit connected to a primary winding of a power conversion transformer (transformer), and the switching output is produced at a secondary winging of the voltage conversion transformer. A voltage induced in the secondary winging with switching operation of the switching circuit is rectified by a rectifier circuit, then converted into a DC voltage by a smoothing circuit, and then outputted.
In this type of switching power supply unit, excessive surge voltage has been sometimes applied to rectifier elements in the rectifier circuit due to inductance of a line between the rectifier elements and windings of the transformer. When such excessive surge voltage is induced, heat generation by the rectifier elements is increased, in addition, power loss is increased, leading to reduction in circuit efficiency.
Thus, for example, Japanese Unexamined Patent Publication No. 2002-165453 proposes a switching power supply unit in which rectifier diodes are fixed integrally with a rectangular conductor line configuring a secondary coil so as to suppress heat generation or power loss in the rectifier diodes.